1-SUBSTITUTED 1-ETHOXY DIENES OBTAINED BY REACTION OF 1,1-DIETHOXYBUT-2-ENE WITH ELECTROPHILES IN THE PRESENCE OF THE MIXED-METAL BASE LICKOR

The mixture of sec-butyllithium and potassium tert-butoxyde (LICKOR re agent) in THF at -95 degrees C, promotes smooth 1,4-eliminative proces s in 1,1-diethoxybut-2-ene (1) to afford conjugate (E)-1-ethoxybuta-1- 3-diene (2). Moreover, when 2 equivalents of the mixed base are sued f or 1 equivalent of the substrate, further metallation of the derivativ e 2 takes place affording the corresponding alpha-substituted derivati ves 4a-e. Intermediates 4b-c and 4e can be converted by aqueous methan olic hydrochloric acid into the corresponding carbonyl compounds 5b-c and 5e. On the other hand, in mild acid rt-butyl-4-ethoxy-2,2-dimethyl thepta-4,6-dien-3-ol (4d) cyclizes in a one-pot synthetic sequence to 2-di-tert-butyl-3-ethoxy-5-methyl-2,5-dihydrofuran (5d).